Environmental Measurement While Drilling System for Real-Time Field Screening of Contaminants

Sampling during environmental drilling is essential to fully characterize the spatial distribution and migration of subsurface contaminants. However, analysis of the samples is expensive and time-consuming: off-site laboratory analysis can take weeks or months. Real-time information on environmental conditions, drill bit location and temperature during drilling is valuable in many environmental restoration operations. This type of information can be used to provide field screening data and improved efficiency of site characterization activities. The Environmental Measurement-While-Drilling (EMWD) System represents an innovative blending of new and existing technology in order to obtain real-time data during drilling. The system consists of two subsystems. The down-hole subsystem (at the drill bit) consists of sensors, a power supply, a signal conditioning and transmitter board, and a radio-frequency (RF) coaxial cable. The up-hole subsystem consists of a battery pack/coil, pickup coil, receiver, and personal computer. The system is compatible with fluid miser drill pipe, a directional drilling technique that uses minimal drilling fluids and generates little to no secondary waste. In EMWD, downhole sensors are located behind the drill bit and linked by a high-speed data transmission system to a computer at the surface. Sandia-developed Windowstrademark-based software is used for data display and storage. As drilling is conducted, data is collected on the nature and extent of contamination, enabling on-the-spot decisions regarding drilling and sampling strategies. Initially, the downhole sensor consisted of a simple gamma radiation detector, a Geiger-Mueller tube (GMT). The design includes data assurance techniques to increase safety by reducing the probability of giving a safe indication when an unsafe condition exists. The EMWD system has been improved by the integration of a Gamma Ray Spectrometer (GRS) in place of the GMT. The GRS consists of a sodium iodide-thallium activated crystal coupled to a photomultiplier tube (PMT). The output of the PMT goes to a multichannel analyzer (MCA).The MCA data is transmitted to the surface via a signal conditioning and transmitter board similar to that used with the GMT. The EMWD system is described and the results of the GRS field tests and field demonstration are presented